The present invention relates to a control apparatus for an engine, and particularly to, a control apparatus for attaining reduction in exhaust emissions in startup of the engine.
In recent years, associated with tightening of regulations on exhaust emissions from vehicle engines, further reduction in engine exhaust emissions is being demanded in all countries of the world such as the United States, Europe and Japan.
Conventionally, it is known that the retarding of the ignition timing is available to reduce exhaust amount of hydrocarbons before activation of catalysts. Meanwhile, it is also known that when the retarding is performed, combustion condition (operating condition of an engine) is unstable.
Japanese Patent Application Publication JP-A-8-122099 discloses a control apparatus that compares a predetermined threshold to a deviation amount between an average angular acceleration in all cylinders and an average angular acceleration in each of the cylinders, and that corrects an ignition timing in an idle operation.
The a control apparatus of JP-A-8-12209 is based on the assumption that the engine is in an idle operation state. Further, since the ignition timing is corrected based on the results of a statistical processing (average calculation), a correction speed tends to get slow. Accordingly, as described above, it is difficult to apply the technique of JP-A-8-12209 to an extremely early stage in startup of engine from a first combustion to a start of the idle operation and, therefore, the exhaust emissions are considered not to be reduced yet.
In addition to the above, Japanese Patent Application Publications. JP-A-9-100741 and JP-A-2-064252 also disclose similar control apparatus. In the same manner as in the above, any of the inventions are based on the assumption that the engine is in an idle operation state. Further, since the ignition timing is corrected based on the results of a statistical processing (average calculation), the above-described problem is considered not to be solved yet.